Arsenal needed Kai Havertz's late winner to go top of the Premier League by beating Brentford 2-1 on Saturday as Manchester United kept alive their faint hopes of finishing in the top four with a 2-0 win over Everton.
Liverpool's blockbuster clash against Manchester City at Anfield on Sunday gave the Gunners the chance to edge ahead in the title race.
An eighth consecutive Premier League win took Mikel Arteta's men one point ahead of Liverpool and two clear of defending champions City.
But they had to overcome a glaring error from Aaron Ramsdale on his return to the Arsenal goal.
All seemed to be going to plan for the home side when Declan Rice continued his fine goalscoring form by heading in Ben White's cross on 19 minutes.
However, there was a sting in the tale in a moment Ramsdale will want to forget in first-half stoppage time.
The England international was making just his second Premier League start since September as the on-loan David Raya was ineligible to feature against his parent club.
Ramsdale's lack of match sharpness may have been a factor as he dallied on the ball as his attempted clearance ricocheted off Yoane Wissa into the net.
The Arsenal goalkeeper bounced back after the break to make vital saves from Ivan Toney's spectacular effort and Nathan Collins' header.
Havertz then bulleted home a header from another White cross four minutes from time.
"Massive win for us. These points were so important for us and you could see that in the second half," said Havertz.
"We didn't play our best in the first half but it's even better to win it this way."
GARNACHO SPARK FOR MAN UTD
Everton were made to pay for conceding two first-half penalties as Bruno Fernandes and Marcus Rashford scored from the spot.
Erik ten Hag's team are now eight points adrift of fourth-placed Aston Villa and three behind Tottenham in fifth, who face each other on Sunday, in the race to qualify for next season's Champions League.
"We need wins," said Ten Hag. "We're still in the hunt but it depends on them.
"We have to win our games but we know, in the Premier League, everyone is killing everyone."
Everton sit four points above the relegation zone as their winless league run extended to 11 games.
Alejandro Garnacho was the difference maker at Old Trafford as his quick feet twice provoked spot-kicks.
James Tarkowski was the first Everton defender lured into a mistimed challenge on Garnacho after 10 minutes and Fernandes rolled home his eighth goal of the season.
Garnacho danced through a series of challenges in the 36th minute before he was chopped down by Ben Godfrey.
Fernandes passed over penalty duties to Rashford and Jordan Pickford was unable to deny the forward, who fired home his fifth goal in nine league games.
LUTON EARN PRICELESS POINT
Third bottom Luton rescued a priceless 1-1 draw at Crystal Palace thanks to Cauley Woodrow's last-gasp leveller.
Oliver Glasner's side struck in the 11th minute when Daniel Munoz teed up Jean-Philippe Mateta to flick home.
But Woodrow levelled from Andros Townsend's cross six minutes into stoppage-time to leave Luton three points from safety.
Sheffield United moved off the bottom of the table but blew a two-goal lead as Bournemouth hit back to rescue a 2-2 draw at the Vitality Stadium.
Bournemouth's Dominic Solanke missed a 14th minute penalty as the striker slipped in his run-up and ballooned the spot-kick over the bar.
Gustavo Hamer and Jack Robinson struck to put the Blades into a shock lead.
But Dango Ouattara got one back with a header from a 74th minute corner and Bournemouth equalised in stoppage-time when Enes Unal stabbed home to claim his first goal for the club.
Wolves improved their prospects of qualifying for Europe next season with a 2-1 win against Fulham at Molineux to climb up to eighth.